﻿#region Imported Libraries
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.IO.Compression;
#endregion

namespace org.webguvenligi.NSecureImageLib.GraphicFileFormats.Utilities
{
    public sealed class Crc32Hash
    {
        readonly static uint CrcSeed = 0xFFFFFFFF;

        readonly static uint[] CrcTable = new uint[] {
			0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419,
			0x706AF48F, 0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4,
			0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07,
			0x90BF1D91, 0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
			0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7, 0x136C9856,
			0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
			0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4,
			0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
			0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3,
			0x45DF5C75, 0xDCD60DCF, 0xABD13D59, 0x26D930AC, 0x51DE003A,
			0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599,
			0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
			0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190,
			0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F,
			0x9FBFE4A5, 0xE8B8D433, 0x7807C9A2, 0x0F00F934, 0x9609A88E,
			0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
			0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED,
			0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
			0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3,
			0xFBD44C65, 0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
			0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A,
			0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5,
			0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA, 0xBE0B1010,
			0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
			0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17,
			0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6,
			0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615,
			0x73DC1683, 0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
			0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1, 0xF00F9344,
			0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
			0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A,
			0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
			0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1,
			0xA6BC5767, 0x3FB506DD, 0x48B2364B, 0xD80D2BDA, 0xAF0A1B4C,
			0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF,
			0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
			0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE,
			0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31,
			0x2CD99E8B, 0x5BDEAE1D, 0x9B64C2B0, 0xEC63F226, 0x756AA39C,
			0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
			0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B,
			0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242,
			0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1,
			0x18B74777, 0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
			0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45, 0xA00AE278,
			0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7,
			0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC, 0x40DF0B66,
			0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
			0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605,
			0xCDD70693, 0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8,
			0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B,
			0x2D02EF8D
		};

        internal static uint ComputeCrc32(uint oldCrc, byte value)
        {
            return (uint)(Crc32Hash.CrcTable[(oldCrc ^ value) & 0xFF] ^ (oldCrc >> 8));
        }

        /// <summary>
        /// The crc data checksum so far.
        /// </summary>
        uint crc;

        /// <summary>
        /// Returns the CRC32 data checksum computed so far.
        /// </summary>
        public long Value
        {
            get
            {
                return (long)crc;
            }
            set
            {
                crc = (uint)value;
            }
        }

        /// <summary>
        /// Resets the CRC32 data checksum as if no update was ever called.
        /// </summary>
        public void Reset()
        {
            crc = 0;
        }

        /// <summary>
        /// Updates the checksum with the int bval.
        /// </summary>
        /// <param name = "value">
        /// the byte is taken as the lower 8 bits of value
        /// </param>
        public void Update(int value)
        {
            crc ^= CrcSeed;
            crc = CrcTable[(crc ^ value) & 0xFF] ^ (crc >> 8);
            crc ^= CrcSeed;
        }
        /// <summary>
        /// Resets The Crc And Updates With The Provided Buffer
        /// </summary>
        /// <param name="buffer"></param>
        public void ResetAndUpdate(byte[] buffer)
        {
            this.Reset();
            this.Update(buffer);
        }
        /// <summary>
        /// Resets The Crc And Updates With The Provided Buffer
        /// </summary>
        /// <param name="value"></param>
        public void ResetAndUpdate(int value)
        {
            this.Reset();
            this.Update(value);
        }
        /// <summary>
        /// Resets The Crc And Updates With The Provided Buffer
        /// </summary>
        /// <param name="buffer"></param>
        /// <param name="offset"></param>
        /// <param name="count"></param>
        public void ResetAndUpdate(byte[] buffer, int offset, int count)
        {
            this.Reset();
            this.Update(buffer, offset, count);
        }
        /// <summary>
        /// Updates the checksum with the bytes taken from the array.
        /// </summary>
        /// <param name="buffer">
        /// buffer an array of bytes
        /// </param>
        public void Update(byte[] buffer)
        {
            if (buffer == null)
            {
                throw new ArgumentNullException("buffer");
            }

            Update(buffer, 0, buffer.Length);
        }

        /// <summary>
        /// Adds the byte array to the data checksum.
        /// </summary>
        /// <param name = "buffer">
        /// The buffer which contains the data
        /// </param>
        /// <param name = "offset">
        /// The offset in the buffer where the data starts
        /// </param>
        /// <param name = "count">
        /// The number of data bytes to update the CRC with.
        /// </param>
        public void Update(byte[] buffer, int offset, int count)
        {
            if (buffer == null)
            {
                throw new ArgumentNullException("buffer");
            }

            if (count < 0)
            {
                throw new ArgumentOutOfRangeException("count", "Count cannot be less than zero");
            }

            if (offset < 0 || offset + count > buffer.Length)
            {
                throw new ArgumentOutOfRangeException("offset");
            }

            crc ^= CrcSeed;

            while (--count >= 0)
            {
                crc = CrcTable[(crc ^ buffer[offset++]) & 0xFF] ^ (crc >> 8);
            }

            crc ^= CrcSeed;
        }
        public byte[] CrcByteArray
        {
            get
            {
                byte b1 = Convert.ToByte(crc >> 24);
                byte b2 = Convert.ToByte(b1 << 8 ^ crc >> 16);
                byte b3 = Convert.ToByte(((crc >> 16 << 16) ^ (crc >> 8 << 8)) >> 8);
                byte b4 = Convert.ToByte((crc >> 8 << 8) ^ crc);
                return new byte[] { b1, b2, b3, b4 };
            }
        }
    }
//    public sealed class Crc32Hash : System.Security.Cryptography.HashAlgorithm
//    {
//        private uint data = 0xFFFFFFFF;
//        private readonly static uint CrcSeed = 0xFFFFFFFF;

//        public void UpdateCrc32(byte[] array)
//        {
//            UpdateCrc32(array, 0, array.Length);
//        }
//        public void UpdateCrc32(byte[] array, int ibStart, int cbSize)
//        {
//            HashCore(array, ibStart, cbSize);
//        }

//        public byte[] HashFinalize()
//        {
//            return HashFinal();
//        }

//        protected override void HashCore(byte[] array, int ibStart, int cbSize)
//        {
//            data ^= CrcSeed;
//            for(int n=ibStart; n<ibStart + cbSize; n++)
//                data = CrcTable[(data ^ array[n]) & 0xff] ^ (data >> 8);
//            data ^= CrcSeed;
//        }
//        public override int HashSize
//        {
//            get
//            {
//                return 32;
//            }
//        }
//        protected override byte[] HashFinal()
//        {
//            byte b1 = Convert.ToByte(data >> 24);
//            byte b2 = Convert.ToByte(b1 << 8 ^ data >> 16);
//            byte b3 = Convert.ToByte(((data >> 16 << 16) ^ (data >> 8 << 8)) >> 8);
//            byte b4 = Convert.ToByte((data >> 8 << 8) ^ data);
//            return new byte[] { b1, b2, b3, b4 };
//        }
//        public override void Initialize()
//        {
//            data = 0xFFFFFFFF;
//        }
//        private readonly static uint[] CrcTable = new uint[] {
//            0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419,
//            0x706AF48F, 0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4,
//            0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07,
//            0x90BF1D91, 0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
//            0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7, 0x136C9856,
//            0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
//            0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4,
//            0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
//            0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3,
//            0x45DF5C75, 0xDCD60DCF, 0xABD13D59, 0x26D930AC, 0x51DE003A,
//            0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599,
//            0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
//            0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190,
//            0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F,
//            0x9FBFE4A5, 0xE8B8D433, 0x7807C9A2, 0x0F00F934, 0x9609A88E,
//            0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
//            0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED,
//            0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
//            0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3,
//            0xFBD44C65, 0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
//            0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A,
//            0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5,
//            0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA, 0xBE0B1010,
//            0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
//            0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17,
//            0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6,
//            0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615,
//            0x73DC1683, 0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
//            0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1, 0xF00F9344,
//            0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
//            0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A,
//            0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
//            0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1,
//            0xA6BC5767, 0x3FB506DD, 0x48B2364B, 0xD80D2BDA, 0xAF0A1B4C,
//            0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF,
//            0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
//            0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE,
//            0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31,
//            0x2CD99E8B, 0x5BDEAE1D, 0x9B64C2B0, 0xEC63F226, 0x756AA39C,
//            0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
//            0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B,
//            0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242,
//            0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1,
//            0x18B74777, 0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
//            0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45, 0xA00AE278,
//            0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7,
//            0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC, 0x40DF0B66,
//            0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
//            0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605,
//            0xCDD70693, 0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8,
//            0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B,
//            0x2D02EF8D
//};
//    }
    /// <summary>
    /// Crc32 Class For Png Checksum Calculations
    /// </summary>
    public static class Crc32
    {
        public static bool AreCrc32sEqual(byte[] bufferForCrcCalcuation, byte[] crcValueToBeCompared)
        {
            byte[] calculatedCrc = GetCrc(bufferForCrcCalcuation);
            return calculatedCrc.CompareByteArray(crcValueToBeCompared);
        }
        /// <summary>
        /// Calculates an array of 4 bytes containing the calculated CRC.
        /// </summary>
        /// <param name="buf">The raw data on which to calculate the CRC.</param>
        public static byte[] GetCrc(byte[] buffer)
        {
            Crc32Hash tempHash = new Crc32Hash();
            tempHash.ResetAndUpdate(buffer);
            return tempHash.CrcByteArray;
        }
    }
}
